Context-aware congestion control for pedestrian safety communication

Abstract

Pedestrian-to-Everything (P2X) communication has numerous advantages from improving traffic light cycle schedules to increase pedestrian safety. Challenges, such as handling the lack of positioning accuracy in urban canyons, limited battery power, and wireless channel resources, still need to be addressed before mass deployment of these systems. The goal of this research is to introduce a distributed channel congestion control algorithm for Personal Safety Messages (PSMs) that can converge in heterogeneous application environments with different message rates. Different message rates arise, for example, with contextual transmission policies (CTP) that activate different applications based on situational context, such as the estimated positioning accuracy. Energy consumption is another challenge when smartphones are used to enhance pedestrian safety. Therefore, to minimize channel sensing energy usage, we further propose a novel collaborative channel load measurement mechanism, as opposed to more conventional approaches employed in Vehicle-to-Vehicle (V2V) communication.To properly tackle the problem, an accurate network simulator is important to understand how P2X communication performs for different algorithms and approaches. More specifically, the aforementioned simulator needs to accurately model the following components: (i) Channel propagation with co-channel interference in 5.9~GHz band with 10 MHz bandwidth, (ii) realistic positioning model as part of the system, i.e. smartphones, that P2X transmissions take place, and (iii) realistic dense mobility scenarios. Therefore, we start with modeling and calibrating channel propagation for Dedicated Short-Range Communications (DSRC) in the 5.9 GHz DSRC band in an intersection environment. Then, we evaluate channel performance under an idealized positioning accuracy for a realistic mobility scenario. Then, the steps taken to investigate different approaches to reduce unnecessary P2X transmissions are shown. Finally, we develop a multi-rate congestion controller that improves smartphones battery consumption and information age. Extensive simulations show that when the proposed algorithms are used, information age for P2X safety applications is improved, which potentially increases pedestrian safety, and the energy consumption is significantly reduced.